Electric switch having a flexible contact element



y 1966 c. R. RADLOFF ETAL 3,253,109

ELECTRIC SWITCH HAVING A FLEXIBLE CONTACT ELEMENT 2 Sheets-Sheet 1 Filed April 10, 1964 x f z.

IN VEN'TORS Car/XNFad/off' BY Ar/ Sam/Mn H ORNE Y May 24, 1966 c. R. RADLOFF ETAL 3,253,109

ELECTRIC SWITCH HAVING A FLEXIBLE CONTACT ELEMENT Filed April 10, 1964 2 Sheets-Sheet 2 f INVENTORS ar/ i3 Rad/0f? 5 BY lVar/ 5amf kn I? TORNEY United States Patent ()fi ice V 3,253,1as Patented May 24, 1966 3,253,109 ELECTRIC SWITCH HAVING A FLEXIBLE C(lNTACT ELEMENT Carl R. Radlotf, Grand Rapids, and Karl Sarafian, Lathrup Village, Mich, assiguors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Apr. 10, 1964, Ser. No. 358,825 8 Claims. (Cl. 200-166) This invention relates to an electric switch having unique applicability with high-power electrical equipment such as dielectric embossing presses.

As is well known, a dielectric embossing press consists of a power section, oscillator section, and work section. The function of the power section is to convert low voltage, alternating current from the plant supply lines into high voltage, direct current. The oscillator then changes the high voltage, direct current into high voltage, radio frequency, alternating current, which is then converted into heat energy in the thermoplastic material being embossed between a pair of vertically-spaced electrodes located in the work section.

During the heat cycle portion of a dielectric embossing process, a high frequency alternating voltage between 1 and 200 megacycles is applied between the electrodes to generate heat directly within the thermoplastic material. As should be apparent, high frequency electrical waves in the range indicated could interfere with radio and television reception in the surrounding plant area unless some precautions were taken to prevent this from occurring. To this end, all high power dielectric embossing presses are customarily provided with shielding around the work section which prevents the high frequency oscillator output from causing radio interference during the embossing cycle. Typically, this shielding consists of elongated vertical sheets of metal that encompass the electrodes connected with the stationary and movable press portions. The arrangement is such that when the press is in the open position the shielding portions which surround the respective electrodes are disengaged and locate-d in non-interfering positions so that the material to be embossed can be readily inserted or removed from the work section by the press operator. On the other hand, when the press is closed the opposed shielding portions contact each other to completely enclose the work section and provide an electrical connection for carrying high amperage electric current. In other words, not only does the shielding serve to confine the high frequency alternating voltage within the press but in addition serves as a switch means in the electric circuit of the dielectric embossing press.

One problem with the shielding of the above-described type, however, is that when utilized with high power output dielectric embossing presses, the switch portions of the shielding tend to weld together between the contacting surfaces thereof. For the most part, this can be primarily attributed to the poor surface contact heretofore realized between the switch contacts incorporated with the shielding.

Accordingly, the principal object of this invention is to provide an electric switch having good surface contact characteristics so as to permit it to carry electrical current of a high magnitude.

Another object of this invention is to provide an electric switch which can he incorporated with shielding normally utilized on dielectric embossing presses.

The above objects and others are accomplished in accordance with the invention with an electric switch comprising stationary and movable contact members, one of which includes a pair of spaced parallel blades. The other of the contact members has a flexible contact element electrically and mechanically connected thereto so as to form a cavity which in cross section is completely enclosed. The cavity is filled with a resilient material such as rubber and means are provided for moving the movable contact member into engagement with the stationary contact member so that the flexible contact element engages the parallel blades and is deformed against the resilient means to increase the effective contact area between the contact members.

A more complete understanding of this invention can be derived from the following description and the accompanying drawings in which:

FIGURE 1 illustrates in block form a dielectric embossing press of the type with which this invention can be incorporated;

FIGURE 2 is an enlarged sectional view taken on lines 2-2 of FIGURE 1 and illustrates the shielding members incorporating an electric switch made in accordance with the invention;

FIGURE 3 is a perspective view similar to that shown in FIGURE 2 with the switch in the open position;

FIGURE 4 is an enlarged view taken on lines 4-4 of FIGURE 1 and illustrates the form of shielding employed by the dielectric embossing press of FIGURE 1, and

FIGURE 5 is a schematic diagram illustrating the electric circuit and various components of the dielectric embossing press of FIGURE 1.

Referring now to FIGURE 1, a dielectric embossing press 10 is shown having an oscillator section 12 and a work section 14 which includes upper and lower shielding sections 16 and 18 located in the positions assumed when the press is closed. As best seen in FIGURE 2 and the schematic diagram of FIG. 5, the respective shielding sections are located adjacent to an upper stationary electrode 20 and a lower movable electrode 22 which in this instance is equipped with a plurality of elongated embossing blades 24. An air or hydraulic cylinder 26 is connected to the lower electrode 22 for moving the latter upwardly towards the upper electrode 20 to close the press. Thus, assuming a sandwich of thermoplastic material to be embossed is located between the electrodes and the press is closed as described, a pressure can be imposed upon the materials during the heat cycle. Moreover, when the press is closed, the shielding sections 16 and 18 engage each other so as to complete the electric circuit. In this connection, it should be noted that for illustrative purposes, the shielding sections constitute the sole switch means in the electric circuit of FIGURE 5. In actual practice, however, a primary switch is usually interposed in the line between the oscillator 12 and the section 16 so that the shielding serves as a secondary switch means.

As seen in FIG. 4, the shielding section 18 consists of four straight metal sheet portions located in rectangular form so as to completely surround the lower electrode 22. The lower end of the shielding section 18 is mechanically and electrically connected to a support 27 which carries electrode 22. As shown in FIG. 2, the upper end 28 of shielding section 18 terminates with a flexible contact portion 30 that constitutes one part of the electric switch made in accordance with the invention. More specifically, the contact portion 30 comprises a flexible braided conductor 32 which extends the full length of each straight part of the shielding section 18 and is looped about a co-extensive elongated U-shaped support 34 cemented to the upper end of the shielding section. The conductor 32 is preferably made from a plurality of braided wires of a low resistance metal such as copper and has the opposite ends 36 and 38 thereof rigidly secured to the shielding section 18 by a plurality of fasteners such as the screw and nut combination indicated by the numeral 40; Although not shown, the

3 fasteners are provided at spaced points along the length of the shielding and serve to establish an electrical connection between the braided conductor 32 and the shielding section 18.

In the preferred form shown in FIGURE 3, the support 34 is made from a resilient material such as rubber and is constructed so that its upper end has inclined intersecting surfaces 42 and 44 which provide a somewhat pointed leading edge 45. Similarly, each leg of the support 34 has inwardly inclined surfaces 46 and 48 so that together with the surfaces 42 and 44 a pair of oppositely disposed parallel flat surfaces 50 and 52 are defined. Thus the surfaces 50 and 52 cause the conductor 32 to have parallel contact surfaces 54 and 56 which in the disengaged position have an effective height, as indicated by the letter y.

The shielding section 16, which constitutes the stationary contact member of this switch, is formed in four straight sections about the upper electrode 20 in a rectangular fashion similar to the shielding section 18. As seen in FIGURE 2, the shielding section 16 is located in vertical alignment with the shielding section 18 and comprises a pair of elongated parallel metal blades 58 and 60 rigidly connected to a spacer 62 which in turn is bolted to the fixed upper portion of the press adjacent the electrode 20. The blades 58 and 60 are respectively provided with inner contact surfaces 64 and 66 which are spaced apart a distance less than the overall width of the contact member 30. In addition, the lower inner ends 68 and 70 of the blades are rounded in order to provide easy access for the contact member 30. Thus, when the press is closed the contact member 30 moves from the position indicated by the phantom lines into the area between the blades 58 and 60 and the braided conductor 32 is compressed against the rubber base 34. As a result, the support 34 is deformed so that the distance between the surfaces 50 and 52 is decreased. In addition, a shortening in length occurs in the inclined surfaces 42, 44, 46, and 48 when viewed in cross section with a resultant increase in vertical height of surfaces 50 and 52. Inasmuch as the latter surfaces define the contact area of the conductor 32, the contact surfaces 54 and 56 enjoy a corresponding increase in height and accordingly an increase in effective contact surface for engaging the blades contact surfaces 64 and 66.

From the above, it should be apparent that the abovedescribed switch lends itself well for use in circuit where large currents are carried. Moreover, in cases where the contact portions of the switch are of an extended length, any irregularities occurring between the spacing of the blades can be compensated for through the deforming action on the flexible contact member. Hence,

good electrical contact is assured the full extent of the engaging parts of the switch so that the problem of arcing and welding is eliminated between the contacting surfaces.

Various changes and modifications in the abovedescribed switch can be made without departing from the invention. Such changes and modifications are contemplated, and therefore it should be understood that we do not intend to be limited except by the scope of the following claims. I

What is claimed is:

1. An electric switch comprising elongated stationary and movable contact members, one of said contact members having an elongated flexible contact element electrically and mechanically connected to the associated contact member so as to form a cavity which in cross section is completely enclosed, the other of said contact members having an elongated rigid contact surface, a rubber support substantially filling said cavity, and means for pressing the flexible contact element into engagement with the rigid contact surface so that the flexible contact element is deformed against the resilient means to increase the effective surface contact area between the members.

2. An electric switch comprising stationary and movable contact members, one of said contact members comprising a flexible element electrically and mechanically connected thereto so as to form a cavity which in cross section is completely enclosed, a portion of the outer surface of said element serving as a flexible contact surface, the other of said contact members having a rigid contact surface, resilient means in said cavity engaging all points of the inner surface of said portion, and means for pressing the flexible contact surface into engagement with the rigid contact surface so that the element is deformed against the resilient means to increase the effective surface contact area between the members.

3. An electric switch comprising stationary and movable contact members, one of said contact members comprising a pair of spaced parallel blades, the other of said contact members having a pair of oppositely disposed fiexible contact surfaces electrically and mechanically connected thereto, resilient means carried by said other of said contact members and causing said flexible contact surfaces to be spaced apart a distance greater than the spacing between said blades, and means for moving the movable contact member into engagement with said stationary member so that said flexible contact surfaces are located between the blades and the resilient means is compressed to increase the effective surface contact area of the flexible contact surface.

4. An electric switch comprising stationary and movable contact members, one of said contact members comprising a pair of spaced parallel blades, the other of said contact members having a flexible element in the form of a loop with the opposite ends electrically and mechanically connected to said other contact member, resilient means substantially filling said loop and causing said flexible element to have opposite contact surfaces spaced apart a distance greater than the spacing between said blades, and means for moving the movable contact member into engagement with said stationary member so that said contact surfaces of the flexible element are located between the blades and the resilient means is compressed to increase the effective surface contact area of the flexible contact surface.

5. An electric switch for a dielectric embossing press having vertically-spaced movable and stationary electrode members, first and second elongated vertically aligned sheet-like conductor members enclosing the respective electrode members, each of said electrode members being electrically connected with the associated conductor member, one of said conduct-or members having a flexible contact element electrically and mechanically connected thereto so as to form a cavity which in cross section is completely enclosed, the other of said conductor members having a rigid contact surface, resilient means in said cavity, and means for moving said movable electrode member towards said stationary electrode member whereby the flexible contact element engages the rigid contact surface so that the flexible contact element is deformed against said resilient means to increase the effective surface contact area.

6. An electric switch for a dielectric embossing press having vertically-spaced movable and stationary electrode members, first and second elongated vertically aligned sheet-like conductor members enclosing the respective electrode members, each of said electrode members being electrically connected with the associated conductor members, one of said conductor members terminating with a co-extensive flexible contact element, means electrically and mechanically connecting said element to said associated conductor member so as to form a cavity which in cross section is completely enclosed, the other of said conductor members terminating with parallel contact blades spaced a distance less than the width of said element, resilient means in said cavity, and means for moving said movable electrode member towards said stationary electrode member whereby the flexible contact element is positioned between said contact blades and the flexible contact element is deformed against said resilient means to increase the eifective surface contact area.

7. An electric switch for a dielectric embossing press having vertically-spaced movable and stationary electrode members, first and second elongated vertically aligned sheet-like conductor members enclosing the respective electrode members, each of said electrode members being electrically connected with the associated conductor members, one of said conductor members terminating with a co-extensive flexible contact element, means for electrically and mechanically connecting said element to said one of said conductor members so as to form a cavity which in cross section is completely enclosed, the other of said conductor members having a rigid contact surface, resilient means substantially filling said cavity, and means for moving said movable electrode member towards said stationary electrode member whereby the flexible contact element engages the rigid contact sul face so that the flexible contact element is deformed against said resilient means to increase the effective surface contact area.

8. The electric switch of claim 7 wherein said flexible contact element comprises a plurality of braided wires.

References Cited by the Examiner UNITED STATES PATENTS 1,898,901 2/1933 Ru-ppel 200148 3,127,492 3/1964 Date 200-170 KATHLEEN H. CLAFFY, Primary Examiner.

HERMAN O. JONES, Assistant Examiner. 

1. AN ELECTRIC SWITCH COMPRISING ELONGATED STATIONARY AND MOVABLE CONTACT MEMBERS, ONE OF SAID CONTACT MEMBERS HAVING AN ELONGATED FLEXIBLE CONTACT ELEMENT ELECTRICALLY AND MECHANICALLY CONNECTED TO THE ASSOCATED CONTACT MEMBER SO AS TO FORM A CAVITY WHICH IN CROSS SECTION IS COMPLETELY ENCLOSED, THE OTHER OF SAID CONTACT MEMBERS HAVING AN ELONGATED RIGID CONTACT SURFACE, A RUBBER SUPPORT SUBSTANTIALLY FILLING SAID CAVITY, AND MEANS FOR PRESSING THE FLEXIBLE CONTACT ELEMENT INTO ENGAGEMENT WITH THE RIGID CONTACT SURFACE SO THAT THE FLEXIBLE CONTACT ELEMENT IS DEFORMED AGAINST THE RESILIENT MEANS TO INCREASE THE EFFECTIVE SURFACE CONTACT AREA BETWEEN THE MEMBERS. 